CaO hydrated with ethanol solution for flue gas HCl immobilization. Part Ⅰ: Modification & dechlorination

Abstract

To eliminate the harmful chloride ions in the wet flue gas desulfurization (WFGD) device that mainly come from the flue gas and make the WFGD wastewater chloridized and gypsum deteriorated, a novel ethanol-modified CaO dechlorinater for flue gas HCl removal was developed by hydration modification. It features nanosized crystals, well-developed micro- and meso- pores that facilitate a high dechlorination efficiency. The effects of ethanol content, hydrating temperature, space velocity and reaction temperature on removal performance of HCl were explored. The dechlorination efficiency not only relies on the reaction temperature but also on the reaction products that influence the dechlorination process. The saturated chlorine capacity under the optimal temperature of 450 °C reaches 951.22 mg/g. The adsorbent is incompletely chlorinated to CaClOH at 150 °C, the resultant product converts to CaCl2 or CaCl2·2H2O above 300 °C. The ethanol modification mechanism is deduced based on the fact that the ethanol hydration lowers the permittivity of the solution and favors generating nanoparticles and the short-chain ethanol weakens the surface tension that intensifies the bond rupture and enhances the dechlorination.